backups: encrypted backups must have .enc extension

src/apps.js

@@ -176,6 +176,7 @@ const appstore = require('./appstore.js'),
     os = require('os'),
     path = require('path'),
     paths = require('./paths.js'),
+    PassThrough = require('stream').PassThrough,
     reverseProxy = require('./reverseproxy.js'),
     safe = require('safetydance'),
     semver = require('semver'),
@@ -2669,12 +2670,20 @@ async function getBackupDownloadStream(app, backupId) {
 
     const backupConfig = await settings.getBackupConfig();
 
-    return new Promise((resolve, reject) => {
-        storage.api(backupConfig.provider).download(backupConfig, tgz.getBackupFilePath(backupConfig, backup.remotePath), function (error, sourceStream) {
-            if (error) return reject(error);
-            resolve(sourceStream);
-        });
+    const ps = new PassThrough();
+
+    const stream = await storage.api(backupConfig.provider).download(backupConfig, tgz.getBackupFilePath(backupConfig, backup.remotePath));
+    stream.on('error', function(error) {
+        debug(`getBackupDownloadStream: read stream error: ${error.message}`);
+        ps.emit('error', new BoxError(BoxError.EXTERNAL_ERROR, error));
     });
+    stream.pipe(ps);
+
+    const now = (new Date()).toISOString().replace(/:|T/g,'-').replace(/\..*/,'');
+    const encryptionSuffix = backup.encryptionVersion ? '.enc' : '';
+    const filename = `app-backup-${now} (${app.fqdn}).tar.gz${encryptionSuffix}`;
+
+    return { stream: ps, filename };
 }
 
 async function restoreInstalledApps(options, auditSource) {